As captain of a Soviet submarine, Ed Harris may be one of the only reasons to see the overwrought “Phantom.”

Todd Robinson’s “Phantom’’ gives us a couple of things we haven’t seen in a while: the great Ed Harris and a Cold War submarine thriller. It’s not something you want to plunk down $12 for, but just diverting enough to check out when it arrives on Netflix Instant.

This movie adds lots of speculation, and not a few clichés, to the event that “inspired’’ it, the mysterious 1968 sinking of the K-129, a Soviet submarine carrying thermonuclear missiles, in the South Pacific (and a reportedly classified recovery effort by the US).

Like Kenneth Sewell’s 2005 book “Red Star Rogue’’ — not credited as the film’s source — Robinson’s script theorizes that K-129, which he calls the B-67, was commandeered by rogue Soviet nationalists on board who planned to launch a nuclear warhead at US territory.

The rogues’ expectation is that because the submarine used a cloaking device that gives the film its title, the Americans would assume the attack came from a Chinese submarine and this would ignite a Chinese-American nuclear holocaust that would leave the Soviets in control of the world.

Of course, the only thing standing in the way of these fanatic KGB agents — led by a badly miscast David Duchovny — is the stalwart, about-to-be-retired Soviet captain (Harris) who’s been assigned to take out his old submarine for one last spin before it’s sold to the Chinese.

Oh, and the captain is the son of a World War II hero and has some affection for the US because he visited there with his wife, a ballerina, as part of a cultural exchange.

As well, the captain is a guilt-ridden epileptic who self-medicates with booze. He suffers (along with the audience) flashbacks to an earlier accident on the same submarine that resulted in loss of life.

That’s nearly as much baggage as the Titanic, but Harris is the sort of expert actor who can handle the load without buckling. He certainly knows underwater drama from James Cameron’s “The Abyss,’’ in which he was hunting for a Soviet submarine (and ended up finding aliens).

It helps that Harris’ loyal second-in-command, who joins with the captain in trying to foil Duchovny’s plot, is played by the great character actor William Fichtner, who is also too seldom seen these days. (Harris’ “Right Stuff’’ co-star Lance Henriksen turns up briefly as the commander who sends Harris out to sea, then shoots himself.)

Robinson generates a fair amount of suspense in “Phantom,’’ which may be on the talky side but has nicely appointed sets representing the aging sub’s interiors.

The beyond-hokey final sequence would sink a lesser film, but Captain Harris keeps it afloat. I salute the comrade’s sheer professionalism.